• The Vendor's Bazaar forum is for commercial offers and transactions. Only unmoderated members can post here.

    diyAudio provides this forum for the convenience of our members, but makes no warranty nor assumes any responsibility. We do not vet any members. Use of this facility is at your own risk. Customers can post any issues in those threads as long as it is done in a civil manner. All diyAudio rules about conduct apply and will be enforced.

Transformer-fed TDA8932 25W/8R mono amp kits

Jump to Latest
#181
Thanks Richard it was more the trafos I was thinking about getting from you. I'll have a think!
Yes it is amazing how cheap they can get these boards out.
Hhmm I'm not sure ...we.normally get them to bring out whatever they recommend but I also like duck and hoi sin....and salted 🌶 chilli beef. I guess it is more your mainstream Cantonese. I'm pretty sure it isn't very authentic 'Chinese' although they have said it'll be more so in Feb!
 
#182
I've ordered the Chinese trafos...for whatever reason.
Is there much mileage in tweaking the output LC filter. The values you recommend Richard are for 8ohm load as per the NXP datasheet....0.68uF and 22uH for 8r. If we know we use lower impedance speakers woukd we be better off using 1uf and 15mH....or even using those values anyway as a midpoint between the 4e and 8r values?
I see Shertzey used a 1uf SMR but I think he kept the 22uH.....horses for courses I guess, assuming this all effects the FR graph but maybe not so obvious to the ear?
 
#183
If you use lower impedance speakers then yes, you'll lose some HF with the values already on-board. 6ohm speakers call for 15uH/1uF, 4ohm is 10uH/1.5uF. (These values are shown on p24 of the TDA8932B datasheet). I'd not recommend 4ohm speakers because you'll run into current limiting from the regulator (LD1085) at higher levels.
 
#186
AMP-to-11 boards have come in but I'm still ironing out some bugs with the volume control/buffer board. For some strange reason there was hum but only at certain positions of the volume control. For example right at minimum volume, just when you'd expect the signal to extinguish itself, hum suddenly appeared! It turned out the hum was actually oscillation at some very high frequency from the discrete buffers. Ferrite beads and damping resistors to the rescue....
 
#187
Good work Richard. Hope you suss out your hum quickly.
Got my V3 amp boards delivered. I've just 'extracted ' an 8932 chip from one of the blue 'ebay' 8932 amp boards. Branded NXP. Did it by filing my way through the back of the board.! Seems to have been successful, albeit IC untested...no means for that. I do have 5 chips coming from China. Branded NXP on the photos but I guess that doesn't mean much.Atleast no heat was involved so I can't have burnt it up.!
With the regulators as they are designed, what is the maximum input voltage to the system? Or is the output from the 2 regs dependent on the input. I thought not but I ask for confirmation! Does the 24v go unchecked anywhere else.? Having read the schematic quite a lot i think the answer is 'no' but I am no means experienced with this.
 
#188
Thanks Jim, I've yet to come across any fake TDA8932 so I reckon you're good.

As for maximum input voltage its 29V from the spec of the high powered regulator. But that spec is a max in-out voltage so might be a little bit conservative. The 24V input only goes to caps (35V rating) and the inputs of the two regulators.
 
#192
Any news on trafos from Cinemag? We have the site on the PCB for Cinemag's trafo but the pinout we've used is just a guess. We won't get to test whether the guess is correct, is that something you'll be able to do? I have a pair of the Taobao trafos to fit when I get to it, plus we're going to try some Coilcraft clone inductors from Taobao. They actually admit they're not the real thing but I'm curious to see how close they are in practice.

https://item.taobao.com/item.htm?sp...pn3WU&id=567836389647&ns=1&abbucket=20#detail
 
#193
On the J Lester thread there is talk of the Codeca style output inductors sounding good. Like used on the 3e Audio amps.i had a 3e board and found the inductors ran quite hot, where the Coilcraft on the JLE were fairly cool.
Just observations!
 
#195
abraxalito said:
Any news on trafos from Cinemag? We have the site on the PCB for Cinemag's trafo but the pinout we've used is just a guess. We won't get to test whether the guess is correct, is that something you'll be able to do? I have a pair of the Taobao trafos to fit when I get to it, plus we're going to try some Coilcraft clone inductors from Taobao. They actually admit they're not the real thing but I'm curious to see how close they are in practice.

https://item.taobao.com/item.htm?sp...pn3WU&id=567836389647&ns=1&abbucket=20#detail
Click to expand...
Hi Richard, yes I am willing to be a guinea pig. Really looking forward to your thoughts to the +11.
Unfortunately, Cinemag customer service, as someone looking for only a couple of units, is presently lacking in gusto, I have sent another mail, also asking for pinouts, and hope to receive a reply this week, but that may be wishful thinking lol. C'est la vie. Will keep you updated.

Nice day to all
 
#197
Cinemag CM-2560 ordered, with up to a 12 week turn around. Ouch. David, from Cinemag has made it clear that he would prefer to handle "group buy" orders in future, so lets see the results, in distant the future : ))

Did you get a chance to test the +11 boards Richard?

Nice day to all.
 
#200
Hi Jim - I had a trawl around on Ali, didn't find anyone selling SER1390. The nearest equivalent on Ali is SER2918, there are two or three sellers of that but the unit of sale is 10 pieces. Not so handy eh?

Oh wait, this seller is selling them in 2s but not a very attractive price : https://www.aliexpress.com/item/1005001938441411.html These are bigger but we might be able to accommodate them on the next revision, we'll have to see how much space there is.
 
Last edited:
You must log in or register to reply here.
Top Bottom